Engineered wood products such as oriented strand board, fiberboard, and laminated veneer lumber (LVL), are widely used in residential and commercial construction, and are gaining popularity in markets such as materials handling and the manufacturing of upholstered furniture. These products are available in a variety of forms such as oriented strand board panels, medium density fiberboard (MDF), laminated veneer lumber products, and the like.
Engineered wood products are typically manufactured from small pieces of wood and heat-cured adhesives. Oriented strand board panels are manufactured from heat-cured adhesives and rectangular-shaped wood strands that are arranged in cross-oriented layers. These are commonly referred to as engineered structural panels and have uses that include roof sheathing, wall sheathing, and flooring systems for residential home construction. The manufacturing process makes it possible for panel makers to add innovative features such as a slip-resistant texture to panels designed for roof sheathing, or to supply oversized and metric panels.
Exposure to water can cause engineered wood products such as OSB panels, to undergo irreversible thickness swelling. The worst swelling behavior typically observed is on the edges of the panel. Engineered wood panels tend to swell to a greater extent on the exposed edges than in the center. For example, OSB sheets manufactured at a thickness of 720 mils (0.720 inch, 1.829 cm), can actually swell to edge thickness values in excess of 1000 mils (1 inch, 2.54 cm). After drying, these sheets do not recover to their original thickness and instead dry to a swollen edge thickness of about 900 mils.
There are available solutions to the problem of edge swell. Most manufacturers of engineered wood products such as OSB sheets attempt to improve the dimensional stability of the sheet by applying a sealing composition such as a paint-formulation to all four edges of the OSB sheet. Typically, the sealer dries into a hydrophobic film, which binds to the OSB sheet and inhibits the absorption of water into the edge of the sheet. Thus, the edge sealant can help to reduce the degree of edge swell experienced by the sheet when it is exposed to water.
Edge sealants are generally applied to engineered wood products such as OSB sheets at the point of manufacture. It is common for a liquid sealant formulation to be applied to the sheets shortly after manufacture. Typically, the formulation dries rapidly after application to the sheets without the use of heating or ventilation equipment. The application of sealers is considered to be an industry standard which provides esthetic value for general marketing purposes and performance advantages to help protect the water-sensitive panels from moisture and rain during the construction phase of a home.
Most sealant formulations are colored and are applied at a level that imparts a solid, uniform, attractive appearance to the engineered wood product unit. After a sealer is applied to the edges of an engineered wood product and dried it should reduce the thickness swelling that typically occurs if the product is exposed to water. Thus, the sealer should dry to form a film that bonds to the wood product and is relatively elastic so that it can expand and stretch as the wood product swells.
There is a need for improving the methods for protecting engineered wood products, particularly the surfaces and edges of substrates which can be exposed to the elements, e.g., water during transportation to customers.